This invention relates to a high yield synthesis of polyol fatty acid polyesters, sucrose polyesters in particular, via transesterification.
The food industry has recently focused attention on polyol polyesters for use as low calorie fats in food products. As a result of this attention, there is a current need for a high yield synthesis of polyol fatty acid polyesters. Historically, such syntheses have been conducted using a mutual solvent to solubilize a polyol and esters of long-chain fatty acids, thus providing a homogenous reaction medium suitable for catalytic transesterification. One variation of this process, known as the Snell synthesis, has been employed as a means for preparing both poly- and lower esters. However, the solvents heretofore employed in such processes are difficult to separate from the final product and are characteristically toxic, therefore limiting the usefulness of such synthesis in the foods industry. Accordingly, recent efforts have been directed toward the discovery of a high yield synthesis of polyol fatty acid polyesters which does not employ toxic solvents.
Other solvent-free transesterification processes are known in the art.
U.S. Pat. No. 3,521,827 discloses the preparation of sucrose polyesters by means of a solvent-free interesterification using phenyl esters. However, phenol is liberated during the reaction. Phenol is extremely toxic and caustic; contaminates the product; and is difficult to separate. Accordingly, this process does not satisfy current needs for a synthesis of polyol fatty acid polyesters for use in the foods industry.
Feuge, et al., "Preparation of Sucrose Esters by Interesterification", Journal of the American Oil Chemical Society, 47[s], 56-60 (1970), disclose a single stage solvent-free transesterification useful in synthesizing fatty acid esters of sucrose. However, this process is limited to the synthesis of lower esters. It has been experimentally determined that if the sucrose/methyl ester ratio of the Feuge, et al., reaction is lowered by use of excess methyl esters in an effort to synthesize polyesters, the reactants will disproportionate and pecipitate sucrose which then caramelizes to form a brittle, charred waste product. Furthermore, the Feuge, et al. article reports low yields using lower alkyl esters. The more successful Feuge, et al. synthesis uses fatty acid methyl carbitol esters as starting materials. Unfortunately, methyl carbitol is, itself, relatively toxic. Thus, the Feuge, et al. process also fails to satisfy current needs for a synthesis of polyol fatty acid polyesters useful in the foods industry.
It is therefore an object of this invention to provide a high yield synthesis of polyol fatty acid polyester.
It is a further object of this invention to provide a synthesis of polyol fatty acid polyesters which does not employ toxic solvent nor generate difficult-to-remove toxic contaminants.
It is a still further object of this invention to provide a synthesis of polyol fatty acid polyesters in which the reactancts do not disproportionate thereby reducing caramelization of the polyol.
These and other objects are obtained herein as will be seen from the following disclosure.